To Investigate the Effect of Substrate Concentration On Yeast Respiration

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Introduction

TO INVESTIGATE THE EFFECT OF SUBSTRATE CONCENTRATION ON YEAST RESPIRATION This is an experiment to examine how the concentration of the substrate Glucose affects the rate of reaction of the enzyme Yeast. Hypothesis The rate of yeast respiration will increase as the concentration of glucose increases. This is because the active sites of the enzymes in the yeast have fewer substrate molecules to bind with to form an enzyme-substrate complex. Outline Yeast will be suspended in glucose solutions of different concentration in different test tubes. The carbon dioxide produced by respiration of the yeast will be bubbled through the glucose solution and the volume of CO2 produced, used as a measure of the rate of respiration against a given time. A graph will be plotted of the different concentrations against the time taken. ...read more.

Middle

Using the cork borer, take a sample of potato, cut this piece in cm intervals using the scalpel and plastic rule. Then cut these a further 2 sections, so there is now 5 sections per 1cm piece of potato. Using distilled water; allow the potato discs to stick to the side of the glass Thistle Funnel. 2. Fill a beaker with about 4cm of the pre-made measured solution of Glucose and using the graduated measuring cylinder, completely fill the 10 cm3 cylinder with the same solution. 3. Immerse the thistle funnel into the beaker with the steam below the surface of the Glucose over the funnel stem. 4. Measure the volume of oxygen evolved in a time of 5mins. 5. Repeat the procedure with the other Glucose solutions. Be aware not to contaminate each solutions with one another, this will cause inaccurate results. ...read more.

Conclusion

When measuring the volumes of water and Glucose, the measurement should be taken from a 90-degree angle to avoid parallax error. Predictions I predict that as the substrate concentration increases, the rate of reaction will go up at a directionally proportional rate until the solution becomes saturated with the substrate Glucose. When this saturation point is reached, then adding extra substrate will make no difference. The rate steadily increases when more substrate is added because more of the active sites of the enzyme are being used which results in more reactions so the amount of Oxygen released in a given time is higher. Once the amount of substrate molecules added exceeds the number of active sites available then the rate of reaction will no longer go up. This is due to the maximum number of reactions being done at once, so any extra substrate molecules have to wait until some of the active sites become available. ...read more.

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